Regarding Airfoil Speakers for the iPhone, has anyone tried using Simplify Media? I use it to stream/control music from iTunes on my Mac and PC to my iPod Touch. I can also stream my iTunes Library over the internet while I am sitting at Wifi Hotspot. Granted, this solution does not allow you to stream other sources (Pandora, LastFM, Slacker Radio) from your Mac or PC to your iPhone/iPod Touch, but there are apps dedicated to this.

I would definitely love the ability to transmit audio from my Touch to an Airport Express or Apple TV, so here's hoping Apple relaxes their restrictions for App developers.